U.S. patent application number 10/032126 was filed with the patent office on 2002-06-06 for gallium complexes of 3-hydroxy-4-pyrones to treat mycobacterial infections.
Invention is credited to Bernstein, Lawrence R..
Application Number | 20020068761 10/032126 |
Document ID | / |
Family ID | 21863237 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020068761 |
Kind Code |
A1 |
Bernstein, Lawrence R. |
June 6, 2002 |
Gallium complexes of 3-hydroxy-4-pyrones to treat mycobacterial
infections
Abstract
Methods are provided for the use of gallium complexes of
3-hydroxy-4-pyrones in the treatment or prevention of infections
caused by a prokaryote of the genus Mycobacterium, including but
not limited to those infections due to M. tuberculosis and M
leprae. Methods are also provided for the treatment of
immunocompromised patients infected by these and other mycobacteria
species, including species (such as M. avium, M. aurum, and M.
smegmatis) that are not pathogenic to immunocompetent individuals
but may cause disease in immunocompromised patients.
Inventors: |
Bernstein, Lawrence R.;
(Menlo Park, CA) |
Correspondence
Address: |
REED & ASSOCIATES
800 MENLO AVENUE
SUITE 210
MENLO PARK
CA
94025
US
|
Family ID: |
21863237 |
Appl. No.: |
10/032126 |
Filed: |
December 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10032126 |
Dec 20, 2001 |
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09684684 |
Oct 4, 2000 |
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60157460 |
Oct 4, 1999 |
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Current U.S.
Class: |
514/460 ;
514/184 |
Current CPC
Class: |
A61K 45/06 20130101;
C07D 309/40 20130101; A61K 31/7036 20130101; A61N 5/10 20130101;
A61K 31/555 20130101; A61K 31/351 20130101; A61K 33/24 20130101;
A61K 31/7036 20130101; A61K 2300/00 20130101; A61K 31/555 20130101;
A61K 2300/00 20130101 |
Class at
Publication: |
514/460 ;
514/184 |
International
Class: |
A61K 031/35; A61K
031/555 |
Claims
I claim:
1. A method of treating a patient infected by a prokaryote of the
genus Mycobacterium by administering a therapeutically effective
amount of a neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone,
where the 3-hydroxy-4-pyrone has the formula: 2wherein R.sup.1,
R.sup.2, and R.sup.3 are independently selected from the group
consisting of hydrogen and a --C.sub.1-6 alkyl group.
2. The method of claim 1 wherein the complex is administered in a
pharmaceutical composition containing a pharmaceutically acceptable
carrier.
3. The method of claim 1 wherein the blood plasma gallium
concentration obtained is in the range of approximately 1 to 5000
ng/mL.
4. The method of claim 3 wherein the blood plasma gallium
concentration obtained is in the range of approximately 100 to 1500
ng/mL.
5. The method of claim 1 wherein the complex is administered
orally.
6. The method of claim 5 wherein the complex is administered in a
dose of approximately 10 to 2500 mg per day.
7. The method of claim 6 wherein the complex is administered in a
dose of approximately 150 to 750 mg per day.
8. The method of claim 7 wherein the complex is administered for
about 30 to 365 days.
9. The method of claim 8 wherein the complex is administered for
about 30 to 180 days.
10. The method of claim 2 wherein the pharmaceutically acceptable
carrier is suitable for oral administration.
11. The method of claim 10 wherein the carrier is a solid.
12. The method of claim 11 wherein the pharmaceutical composition
is in the form of a tablet or capsule.
13. The method of claim 10 wherein the pharmaceutical composition
is encapsulated in a material that does not dissolve until the
small intestine of the individual is reached.
14. The method of claim 10 wherein the carrier is a liquid.
15. The method of claim 1 wherein R.sup.1, R.sup.2, and R.sup.3 are
H.
16. The method of claim 1 wherein R.sup.1 is --CH.sub.3; and
R.sup.2 and R.sup.3 are H.
17. The method of claim 1 wherein R.sup.1 is --C.sub.2H.sub.5; and
R.sup.2 and R.sup.3 are H.
18. The method of claim 1 wherein R.sup.2 is --CH.sub.3; and
R.sup.2 and R.sup.3 are H.
19. The method of claim 2 wherein the pharmaceutical composition
further includes at least one antimicrobial agent selected from the
group consisting of amikacin, aminosalicylic acid, azithromycin,
capreomycin, ciprofloxacin, clarithromycin, clofazimine,
cycloserine, dapsone, erythromycin, ethambutol, ethionamide,
isoniazid, kanamycin, minocycline, ofloxacin, protionamide,
pyrazinamide, rifabutin, rifampicine, rifampin, sparfloxacin,
streptomycin, trimethoprim sulfamethoxazole, tobramycin, and
viomycin, and combinations thereof.
20. The method of claim 19 wherein the pharmaceutical composition
includes one or more agents selected from the group consisting of
ethambutol, isoniazid, pyrazinamide, rifampin, and
streptomycin.
21. The method of claim 1 wherein the Mycobacterium is selected
from the group consisting of M. africanum, M. aurum, M. avium, M.
avium paratuberculosis, M. balnei, M. bovis, M. chelonae, M.
genitalium, M. gallisepticum, M. gastri, M. goodii, M. gordonae, M.
haemophilum, M. intracellulare, M. kansasii, M. leprae, M.
lepraemurium, M. malmoense, M. microti, M. penetrans, M.
platypoecilus, M. pneumoniae, M. scrofulvaeum, M. simiae, M.
smegmatis, M. szulgai, M. terrae-trivial, M. tuberculosis, M.
ulcerans, and M. xenopi.
22. The method of claim 21 wherein the Mycobacterium is M.
tuberculosis.
23. The method of claim 22 wherein about 150 to 750 mg/day of the
complex is administered for about 30 to 180 days.
24. The method of claim 21 wherein the Mycobacterium is M.
leprae.
25. The method of claim 24 wherein about 150 to 750 mg/day of the
complex is administered for about 30 to 365 days.
26. An improved method of treating a patient infected by a
prokaryote of the genus Mycobacterium by administering to the
patient a combination of antimicrobial agents selected from the
group consisting of amikacin, aminosalicylic acid, azithromycin,
capreomycin, ciprofloxacin, clarithromycin, clofazimine,
cycloserine, dapsone, erythromycin, ethambutol, ethionamide,
isoniazid, kanamycin, minocycline, ofloxacin, protionamide,
pyrazinamide, rifabutin, rifampicine, rifampin, sparfloxacin,
streptomycin, trimethoprim sulfamethoxazole, tobramycin, and
viomycin; the improvement comprising administering a
therapeutically effective amount of a neutral 3:1 gallium complex
of a 3-hydroxy-4-pyrone, where the 3-hydroxy-4-pyrone has the
formula: 3wherein R.sup.1, R.sup.2, and R.sup.3 are independently
selected from the group consisting of hydrogen and a
--C.sub.1-6alkyl group.
27. The method of claim 26 wherein the complex is administered in a
pharmaceutical composition containing a pharmaceutically acceptable
carrier.
28. The method of claim 26 wherein the blood plasma gallium
concentration obtained is in the range of approximately 1 to 5000
ng/mL.
29. The method of claim 28 wherein the blood plasma gallium
concentration obtained is in the range of approximately 100 to 1500
ng/mL.
30. The method of claim 26 wherein the complex is administered
orally.
31. The method of claim 30 wherein the complex is administered in a
dose of approximately 10 to 2500 mg per day.
32. The method of claim 31 wherein the complex is administered in a
dose of approximately 150 to 750 mg per day.
33. The method of claim 32 wherein the complex is administered for
about 30 to 365 days.
34. The method of claim 33 wherein the complex is administered for
about 30 to 180 days.
35. The method of claim 27 wherein the pharmaceutically acceptable
carrier is suitable for oral administration.
36. The method of claim 35 wherein the carrier is a solid.
37. The method of claim 36 wherein the pharmaceutical composition
is in the form of a tablet or capsule.
38. The method of claim 35 wherein the pharmaceutical composition
is encapsulated in a material that does not dissolve until the
small intestine of the individual is reached.
39. The method of claim 35 wherein the carrier is a liquid.
40. The method of claim 26 wherein R.sup.1, R.sup.2, and R.sup.3
are H.
41. The method of claim 26 wherein R.sup.1 is --CH.sub.3; and
R.sup.2 and R.sup.3 are H.
42. The method of claim 26 wherein R.sup.1 is --C.sub.2H.sub.5; and
R.sup.2 and R.sup.3 are H.
43. The method of claim 26 wherein R.sup.2 is --CH.sub.3; and
R.sup.1 and R.sup.3 are H.
44. The method of claim 26 wherein the Mycobacterium is selected
from the group consisting of M. africanum, M. aurum, M. avium, M.
avium paratuberculosis, M. balnei, M. bovis, M. chelonae, M.
genitalium, M. gallisepticum, M. gastri, M. goodii, M. gordonae, M.
haemophilum, M. intracellulare, M. kansasii, M. leprae, M.
lepraemurium, M. malmoense, M. microti, M. penetrans, M.
platypoecilus, M. pneumoniae, M. scrofulvaeum, M. simiae, M.
smegmatis, M. szulgai, M. terrae-trivial, M. tuberculosis, M.
ulcerans, and M. xenopi.
45. The method of claim 44 wherein the Mycobacterium is M.
tuberculosis.
46. The method of claim 45 wherein about 150 to 750 mg/day of the
complex is administered for about 30 to 180 days.
47. The method of claim 44 wherein the Mycobacterium is M.
leprae.
48. The method of claim 47 wherein about 150 to 750 mg/day of the
complex is administered for about 30 to 365 days.
49. The method of claim 26 wherein the combination of antimicrobial
agents comprises three or more antimicrobial agents selected from
the group consisting of ethambutol, isoniazid, pyrazinamide,
rifampin, and streptomycin.
50. The method of claim 26, which further comprises administering
one or more nucleoside analogs.
51. The method of claim 50 wherein the nucleoside analogs are
selected from the group consisting of AZT, ddI, ddC, acyclovir,
gancyclovir, and foscarnet.
52. The method of claim 26, which further comprises administering
one or more protease inhibitors.
53. The method of claim 52 wherein the protease inhibitors are
selected from the group consisting of saquinavir, ritonavir,
indinavir, and nelfinavir.
54. The method of claim 26, which further comprises administering
one or more non-nucleoside reverse transcriptase inhibitors.
55. The method of claim 54 wherein the reverse transcriptase
inhibitors are selected from the group consisting of nevirapine and
delavirdine.
56. A method of treating an immunocompromised patient infected by a
prokaryote of the genus Mycobacterium by administering a
therapeutically effective amount of a neutral 3:1 gallium complex
of a 3-hydroxy-4-pyrone, where the 3-hydroxy-4-pyrone has the
formula: 4wherein R.sup.1, R.sup.2, and R.sup.3 are independently
selected from the group consisting of hydrogen and a
--C.sub.1-6alkyl group.
57. The method of claim 56 wherein the complex is administered in a
pharmaceutical composition containing a pharmaceutically acceptable
carrier.
58. The method of claim 56 wherein the blood plasma gallium
concentration obtained is in the range of approximately 1 to 5000
ng/mL.
59. The method of claim 58 wherein the blood plasma gallium
concentration obtained is in the range of approximately 100 to 1500
ng/mL.
60. The method of claim 56 wherein the complex is administered
orally.
61. The method of claim 60 wherein the complex is administered in a
dose of approximately 10 to 2500 mg per day.
62. The method of claim 61 wherein the complex is administered in a
dose of approximately 150 to 750 mg per day.
63. The method of claim 62 wherein the complex is administered for
about 30 to 180 days.
64. The method of claim 63 wherein the complex is administered for
about 30 to 365 days.
65. The method of claim 57 wherein the pharmaceutically acceptable
carrier is suitable for oral administration.
66. The method of claim 65 wherein the carrier is a solid.
67. The method of claim 66 wherein the pharmaceutical composition
is in the form of a tablet or capsule.
68. The method of claim 65 wherein the pharmaceutical composition
is encapsulated in a material that does not dissolve until the
small intestine of the individual is reached.
69. The method of claim 65 wherein the carrier is a liquid.
70. The method of claim 56 wherein R.sup.1, R.sup.2, and R.sup.3
are H.
71. The method of claim 56 wherein R.sup.1 is --CH.sub.3; and
R.sup.2 and R.sup.3 are H.
72. The method of claim 56 wherein R.sup.1 is --C.sub.2H.sub.5; and
R.sup.1 and R.sup.3 are H.
73. The method of claim 56 wherein R.sup.2 is --CH.sub.3; and
R.sup.1 and R.sup.3 are H.
74. The method of claim 57 wherein the pharmaceutical composition
further includes at least one antimicrobial agent selected from the
group consisting of amikacin, aminosalicylic acid, azithromycin,
capreomycin, ciprofloxacin, clarithromycin, clofazimine,
cycloserine, dapsone, erythromycin, ethambutol, ethionamide,
isoniazid, kanamycin, minocycline, ofloxacin, protionamide,
pyrazinamide, rifabutin, rifampicine, rifampin, sparfloxacin,
streptomycin, trimethoprim sulfamethoxazole, tobramycin, and
viomycin, and combinations thereof.
75. The method of claim 74 wherein the pharmaceutical composition
includes three or more agents selected from the group consisting of
isoniazid, rifampin, pyrazinamide, streptomycin, and
ethambutol.
76. The method of claim 56 wherein the Mycobacterium is selected
from the group consisting of M. africanum, M. aurum, M. avium, M.
avium paratuberculosis, M. balnei, M. bovis, M. chelonae, M.
genitalium, M. gallisepticum, M. gastri, M. goodii, M. gordonae, M.
haemophilum, M. intracellulare, M. kansasii, M. leprae, M.
lepraemurium, M. malmoense, M. microti, M. penetrans, M.
platypoecilus, M. pneumoniae, M. scrofulvaeum, M. simiae, M.
smegmatis, M. szulgai, M. terrae-trivial, M. tuberculosis, M.
ulcerans, and M. xenopi.
77. The method of claim 76 wherein the Mycobacterium is M.
tuberculosis.
78. The method of claim 77 wherein about 150 to 750 mg/day of the
complex is administered for about 30 to 180 days.
79. The method of claim 76 wherein the Mycobacterium is M.
leprae.
80. The method of claim 79 wherein about 150 to 750 mg/day of the
complex is administered for about 30 to 365 days.
81. The method of claim 56, which further comprises administering
one or more nucleoside analogs.
82. The method of claim 81 wherein the nucleoside analogs are
selected from the group consisting of AZT, ddI, ddC, acyclovir,
gancyclovir, and foscarnet.
83. The method of claim 56, which further comprises administering
one or more protease inhibitors.
84. The method of claim 83 wherein the protease inhibitors are
selected from the group consisting of saquinavir, ritonavir,
indinavir, and nelfinavir.
85. The method of claim 56, which further comprises administering
one or more non-nucleoside reverse transcriptase inhibitors.
86. The method of claim 85 wherein the reverse transcriptase
inhibitors are selected from the group consisting of nevirapine and
delavirdine.
87. A method of preventing infection by a prokaryote of the genus
Mycobacteria by administering a prophylactically effective amount
of a neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone, where the
3-hydroxy-4-pyrone has the formula: 5wherein R.sup.1, R.sup.2 and
R.sup.3 are independently selected from the group consisting of
hydrogen and a --C.sub.1-6alkyl group.
88. The method of claim 87 wherein the complex is administered in a
pharmaceutical composition containing a pharmaceutically acceptable
carrier.
89. The method of claim 87 wherein the blood plasma gallium
concentration obtained is in the range of approximately 1 to 5000
ng/mL.
90. The method of claim 89 wherein the blood plasma gallium
concentration obtained is in the range of approximately 50 to 1000
ng/mL.
91. The method of claim 87 wherein the complex is administered
orally.
92. The method of claim 91 wherein the complex is administered in a
dose of approximately 10 to 2500 mg per day.
93. The method of claim 92 wherein the complex is administered in a
dose of approximately 20 to 500 mg per day.
94. The method of claim 93 wherein the complex is administered for
about 30 to 180 days.
95. The method of claim 92 wherein the complex is administered in a
dose of approximately 150 to 750 mg per day.
96. The method of claim 95 wherein the complex is administered for
about 30 to 180 days.
97. The method of claim 88 wherein the pharmaceutically acceptable
carrier is suitable for oral administration.
98. The method of claim 97 wherein the carrier is a solid.
99. The method of claim 98 wherein the pharmaceutical composition
is in the form of a tablet or capsule.
100. The method of claim 97 wherein the pharmaceutical composition
is encapsulated in a material that does not dissolve until the
small intestine of the individual is reached.
101. The method of claim 97 wherein the carrier is a liquid.
102. The method of claim 87 wherein R.sup.1, R.sup.2, and R.sup.3
are H.
103. The method of claim 87 wherein R.sup.1 is --CH.sub.3; and
R.sup.2 and R.sup.3 are H.
104. The method of claim 87 wherein R.sup.1 is --C.sub.2H.sub.5;
and R.sup.2 and R.sup.3 are H.
105. The method of claim 87 wherein R.sup.2 is --CH.sub.3; and
R.sup.2 and R.sup.3 are H.
106. The method of claim 87 wherein the Mycobacterium is selected
from the group consisting of M. africanum, M. aurum, M. avium, M.
avium paratuberculosis, M. balnei, M. bovis, M. chelonae, M.
genitalium, M. gallisepticum, M. gastri, M. goodii, M. gordonae, M.
haemophilum, M. intracellulare, M. kansasii, M. leprae, M.
lepraemurium, M. malmoense, M. microti, M. penetrans, M.
platypoecilus, M. pneumoniae, M. scrofulvaeum, M. simiae, M.
smegmatis, M. szulgai, M. terrae-trivial, M. tuberculosis, M.
ulcerans, and M. xenopi.
107. The method of claim 106 wherein the Mycobacterium is M.
tuberculosis.
108. The method of claim 106 wherein the Mycobacterium is M.
leprae.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 09/684,684, filed Oct. 4, 2000, which claims priority to
U.S. Provisional Patent Application Serial No. 60/157,460, filed
Oct. 4, 1999, the disclosures of which are incorporated by
reference herein.
TECHNICAL FIELD
[0002] The present invention relates generally to the treatment or
prevention of intracellular infections. More particularly, the
invention relates to the treatment or prevention of intracellular
infections by bacteria of the genus Mycobacterium, such as
Mycobacterium tuberculosis (which causes tuberculosis) and
Mycobacterium leprae (which causes leprosy), including strains that
are resistant to conventional antimicrobials. The invention
additionally relates to the treatment of immunocompromised patients
infected by these and other mycobacteria species, including species
(such as Mycobacterium avium, Mycobacterium aurum, and
Mycobacterium smegmatis) that are not pathogenic to immunocompetent
individuals but may cause disease in immunocompromised
patients.
BACKGROUND
[0003] Intracellular bacteria of the genus Mycobacterium are
responsible for several serious and debilitating diseases,
including tuberculosis and leprosy. Tuberculosis is a contagious
bacterial infection caused by M. tuberculosis that afflicts
millions of people worldwide. Current treatment regimens involve
the daily administration of three or four antibiotics (e.g.,
combinations of rifampin, isoniazid, streptomycin, ethambutol, and
pyrazinamide) for six to twelve months. Such regimens commonly
produce significant adverse effects and low patient compliance. The
low patient compliance in turn often leads to the development of
drug-resistant strains. There is therefore a need for an improved
method of treating patients suffering from tuberculosis that
involves a simpler and shorter dosing regimen using a low-toxicity
agent; such a regimen should lead to high patient compliance and a
low incidence of emergent drug resistance.
[0004] Leprosy, a debilitating and disfiguring disease that affects
skin and nerve tissue, is caused by M. leprae. The current
treatment for leprosy resembles tuberculosis combination therapy,
comprising administration of three or four antibiotics (e.g.,
combinations of dapsone, rifampin, rifampicine, and clofazimine).
Due to the complexity of the current dosing regimen and its high
expense, patient compliance tends to be low, leading to the
emergence of drug-resistant strains. These problems, as with
tuberculosis, are compounded by the high concentration of leprosy
in developing countries, where medical supplies and education are
commonly in short supply.
[0005] Although mycobacterial species pose serious threats to
healthy individuals, the threats are greater for immunocompromised
patients. These patients, such as those infected by HIV, are highly
susceptible to mycobacterial infections and are less responsive to
conventional combination anti-mycobacterial therapies. Therefore,
there is a need for a more effective method of treating
mycobacterial infections in immunocompromised patients. Further, an
anti-mycobacterial agent must be compatible with ongoing therapies
in these patients.
[0006] Gallium is known to prevent the replication of intracellular
pathogens, including mycobacteria (Olakanmi et al., 1997, "Gallium
inhibits growth of pathogenic mycobacteria in human macrophages by
disruption of bacterial iron metabolism: a new therapy for
tuberculosis and Mycobacterium avium complex?", J Invest Med
45:234A). Without in any way restricting the invention to a
particular mechanism of action, it is thought that gallium exerts
its antibacterial activity through a novel mechanism: interference
with bacterial iron uptake and metabolism through mimicry of ferric
iron. Replicating bacterial cells (as other replicating cells) have
a high iron requirement, due mainly to their need to produce
ribonucleotide reductase (RR), a ferric iron-bearing enzyme
essential for the synthesis of DNA. Gallium is chemically very
similar to ferric iron, and so can be mistakenly taken up by these
cells and incorporated into RR instead of iron. As
gallium-containing RR (or iron-free RR in general) is
nonfunctional, DNA cannot be synthesized and the affected cell
attempting to replicate will ultimately undergo apoptosis.
[0007] In the case of tuberculosis, infecting mycobacteria live
primarily within macrophages, making the bacteria particularly hard
to reach and to treat with most antibacterial compounds.
Macrophages, however, particularly those that are infected,
naturally take up large amounts of iron by overexpressing
transferrin receptor, which binds to the iron transport protein
transferrin. Gallium administered orally as gallium maltolate binds
to transferrin in place of iron, and so can gain entry into the
macrophages and be taken up by the infecting mycobacteria. It is
also possible that gallium administered as gallium maltolate can be
taken up by macrophages and other target tissues by non-transferrin
dependent mechanisms. The therapeutic mechanisms of action for
gallium are discussed by Bernstein (1998), "Mechanisms of
therapeutic activity for gallium", Pharmacol Rev 50:665-682.
[0008] Gallium nitrate has been administered to humans by
intravenous infusion, though with significant potential side
effects such as nephrotoxicity. This is because a significant
fraction of gallium from intravenous gallium nitrate circulates as
the gallate radical (Ga(OH).sub.4.sup.-). Gallate, as a small
charged molecule, is rapidly excreted in the urine and can
transiently reach high concentrations in the kidney, where it can
react to form precipitates (see Webster et al. (1999), "A
pharmacokinetic and phase II study of gallium nitrate in patients
with non-small cell lung cancer", Cancer Chemother Pharmacol 45:
55-58). Free gallium is also unavailable for target cell uptake by
transferrin-dependent mechanisms. In addition, compliance for a
drug requiring slow intravenous infusion, such as intravenous
gallium nitrate, can be problematic over the several months
required for conventional anti-mycobacterial therapy. By contrast,
orally administered gallium maltolate provides a novel, safer, and
potentially more effective alternative to the anti-mycobacterial
agents currently in use or to gallium salts such as gallium nitrate
that require intravenous administration. Due its unique mechanism
of action, and the likely synergy of gallium with other
antibiotics, oral gallium maltolate should also significantly
shorten the course of treatment for mycobacterial infections. Thus,
administration of gallium maltolate provides an improved method of
treating patients suffering from mycobacterial infections, such as
tuberculosis and leprosy, by providing a simpler as well as a
shorter dosing regimen.
SUMMARY OF THE INVENTION
[0009] One aspect of the invention relates to a method of treating
a patient infected by a prokaryote of the genus Mycobacterium by
administering a therapeutically effective amount of a neutral 3:1
gallium complex of a 3-hydroxy-4-pyrone.
[0010] Yet another aspect of the invention relates to an improved
method of treating a patient infected by a prokaryote of the genus
Mycobacterium by administering to the patient a combination of
antimicrobial agents selected from the group consisting of
amikacin, aminosalicylic acid, azithromycin, capreomycin,
ciprofloxacin, clarithromycin, clofazimine, cycloserine, dapsone,
erythromycin, ethambutol, ethionamide, isoniazid, kanamycin,
minocycline, ofloxacin, protionamide, pyrazinamide, rifabutin,
rifampicine, rifampin, sparfloxacin, streptomycin, trimethoprim
sulfamethoxazole, tobramycin, and viomycin; the improvement
comprising administering a therapeutically effective amount of a
neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone.
[0011] Another aspect of the invention pertains to a method of
treating an immunocompromised patient infected by a prokaryote of
the genus Mycobacterium by administering a therapeutically
effective amount of a neutral 3:1 gallium complex of a
3-hydroxy-4-pyrone.
[0012] Yet another aspect of the invention relates to a method of
preventing infection by a prokaryote of the genus Mycobacterium by
administering a prophylactically effective amount of a neutral 3:1
gallium complex of a 3-hydroxy-4-pyrone.
DETAILED DESCRIPTION OF THE INVENTION
[0013] As noted above, the present invention is directed to methods
for treating and preventing infection by pathogenic intracellular
prokaryotes of the genus Mycobacterium using a neutral 3:1 gallium
complex of a 3-hydroxy-4-pyrone.
[0014] Examples of mycobacterial species to which the methods of
the invention find utility include, by way of illustration and not
limitation, M. leprae and M. tuberculosis.
[0015] Prior to discussing this invention in further detail, the
following terms will be defined. Unless defined below, the terms
used herein have their normally accepted meanings.
DEFINITIONS
[0016] As used herein, the following terms have the definitions
given below:
[0017] The term "genus Mycobacterium" is intended to include all
members of that genus including strains that are resistant to
conventional antimicrobials. The term is intended to encompass
species such as M. tuberculosis and M. leprae, as well as species
such as M. avium, M. aurum, and M. smegmatis, which are not
typically pathogenic to healthy or immunocompetent individuals but
that may cause disease in immunocompromised patients. In general,
the mycobacterial species of interest include, by way of
illustration and not limitation, M. africanum, M. aurum, M. avium,
M. avium paratuberculosis, M. balnei, M. bovis, M. chelonae, M.
genitalium, M. gallisepticum, M. gastri, M. goodii, M. gordonae, M.
haemophilum, M. intracellulare, M. kansasii, M. leprae, M.
lepraemurium, M. malmoense, M. microti, M. penetrans, M.
platypoecilus (commonly known as M. marinarum), M. pneumoniae, M.
scrofulvaeum, M. simiae, M. smegmatis, M. szulgai, M.
terrae-trivial, M. tuberculosis, M. ulcerans, and M. xenopi.
[0018] The term "neutral 3:1 gallium complex of a
3-hydroxy-4-pyrone" refers to an electrostatically neutral complex
of Ga.sup.3+ (Ga(III)) and three equivalents of the anionic form of
a 3-hydroxy-4-pyrone, which complex is represented by the formula
[Ga.sup.3+(py.sup.-).sub.3], wherein py.sup.- represents the
anionic form of a 3-hydroxy-4-pyrone as defined below. Because such
complexes do not dissociate to any significant extent in aqueous
solutions maintained at a pH of from about 5 to about 9, these
complexes remain predominantly electrostatically neutral in such
solutions.
[0019] The term "3-hydroxy-4-pyrone" refers to a compound of
Formula 1: 1
[0020] wherein R.sup.1, R.sup.2, and R.sup.3 are independently
selected from the group consisting of hydrogen and a --C.sub.1-6
alkyl group. The --C.sub.1-6 alkyl group can be branched or
unbranched but is preferably unbranched. Suitable --C.sub.1-6 alkyl
groups include, by way of illustration and not limitation, methyl,
ethyl, isopropyl, and n-propyl. Preferred --C.sub.1-6 alkyl groups
are those having 1-3 carbons, in particular, methyl, and ethyl.
Single substitution is preferred, particularly substitution at the
2or the 6-position, with substitution at the 2-position being most
preferred.
[0021] Exemplary compounds encompassed by the term "a
3-hydroxy-4-pyrone" are described below.
[0022] The unsubstituted form of Formula 1 (R.sup.1, R.sup.2, and
R.sup.3 are H) is known as pyromeconic acid.
[0023] Compounds of Formula 1 where R.sup.2 and R.sup.3 are H
include: 3-hydroxy-2-methyl-4-pyrone (R.sup.1 is --CH.sub.3), which
is also known as maltol or larixinic acid; and
3-hydroxy-2-ethyl-4-pyrone (R.sup.1 is --C.sub.2H.sub.5), which is
sometimes referred to as ethyl maltol or ethylpyromeconic acid.
Both of these are preferred for use in the methods of the
invention, in particular 3-hydroxy-2-methyl-4-pyrone.
[0024] Compounds of Formula 1 where R.sup.1 and R.sup.3 are H
include 3-hydroxy-6-methyl-4-pyrone (R.sup.2 is --CH.sub.3).
[0025] The term "an anion of a 3-hydroxy-4-pyrone" refers to a
compound defined in Formula 1 above wherein the hydroxyl proton has
been removed so as to provide for the anionically charged form of
the compound.
[0026] The term "administering" is intended to refer to the oral
administration of any conventional form for the oral delivery of a
pharmaceutical composition to a patient (e.g., human or other
mammal) that results in the deposition of the pharmaceutical
composition into the gastrointestinal tract (including the gastric
portion of the gastrointestinal tract, i.e., the stomach) of the
patient.
[0027] By the term "therapeutically effective" amount of a drug is
meant a nontoxic but sufficient amount of a compound to provide the
desired effect at a reasonable benefit/risk ratio. The desired
effect may be alleviation of the signs, symptoms, or causes of a
disease, or any other desired alteration of a biological system. In
particular, a therapeutically effective amount refers to an amount
of gallium complex administered such that a blood plasma gallium
concentration is obtained that is sufficient to enable treatment or
prevention of the infection of interest. The therapeutically
effective amount necessary to prevent a disease is referred to as
the "prophylactically effective amount".
[0028] The term "therapeutic agent" refers to any additional
therapeutic agent that is co-administered with the neutral 3:1
gallium complex of a 3-hydroxy-4-pyrone in the methods of the
invention. The additional therapeutic agent can be administered by
any route or in any dosage form. Co-administration can be by
simultaneous or subsequent administration. Simultaneous
administration can be in the form of separate or combined dosage
forms, with the caveat that a combined dosage form should be suited
for oral administration since that is the preferred route of
delivery for the neutral 3:1 gallium complex of a
3-hydroxy-4-pyrone.
[0029] The term "treat," as in to "treat" a condition, is intended
to include (1) preventing the condition, i.e., avoiding any
clinical symptoms of the condition, (2) inhibiting the condition,
that is, arresting the development or progression of clinical
symptoms, and/or (3) relieving the condition, i.e., causing
regression of clinical symptoms.
[0030] The term "patient", as in "treatment of a patient", is
intended to refer to an individual animal or human afflicted with
or prone to a condition, disorder, or disease as specified herein,
and typically refers to mammals, particularly humans.
[0031] By "pharmaceutically acceptable" is meant a material that is
not biologically or otherwise undesirable, i.e., the material may
be administered to an individual along with the neutral 3:1 gallium
complex of a 3-hydroxy-4-pyrone (and any additional therapeutic
agents) without causing any undesirable biological effects or
interacting in a deleterious manner with any of the other
components of the pharmaceutical composition in which it is
contained.
[0032] "Optional" or "optionally" means that the subsequently
described circumstance may or may not occur, so that the
description includes instances where the circumstance occurs and
instances where it does not. For example, recitation of an additive
as "optionally present" in a formulation herein encompasses both
the formulation containing the additive and the formulation not
containing the additive.
[0033] The term "immunocompromised patient" is intended to refer to
a patient suffering from an immunodeficiency. This includes a
patient who has an autoimmune disease such as systemic lupus
erythematosus or rheumatoid arthritis, a patient who is infected
with a retrovirus, a patient who is undergoing chemotherapy, a
patient with a genetic mutation that predisposes him or her to an
immunodeficient state, or a patient who is a transplant recipient
taking anti-rejection medications. Retroviruses that may be the
causative agent in producing an immunodeficiency in a patient
include but are not limited to, the human spumavirus, Mason-Pfizer
monkey bovine leukaemia virus, mouse mammary tumor virus, avian
leukosis virus, murine leukemia virus, Rous sarcoma virus, feline
leukemia virus, feline immunodeficiency virus, simian
immunodeficiency virus, human T cell leukemia viral species
("HTLV1", "HTLV2"), and human immunodeficiency virus ("HIV"). Of
particular interest is HIV, which refers to one or more members of
the group of retroviruses that are members of the primate
lentivirus group of the genus Lentiviridae and are capable of
infecting a human, whether or not this capability has been
demonstrated. For example, HIV-1 and HIV-2 are examples of primate
lentiviruses that are known to infect humans. Infection of a human
by a lentivirus that is not named and differs from all known HIV
strains is also considered to be within the scope of the
invention.
[0034] It must be noted that as used herein and in the claims, the
singular forms "a", "and", and "the" include reference to both the
singular and plural unless the context clearly dictates otherwise.
Thus, for example, reference to "a therapeutic agent" in a
formulation includes two or more active agents, reference to "a
carrier" includes two or more carriers, and so forth.
Synthesis And Methodology
[0035] The neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone
useful in the methods of the present invention can be easily
synthesized by methods that are well known in the art. U.S. Pat.
No. 6,004,951 to Bernstein describes the synthesis of neutral 3:1
gallium complexes of the compounds of Formula 1, and is
incorporated herein by reference. In general, the complexes are
synthesized by reacting the desired 3-hydroxy-4-pyrone with gallium
ions in solution. The gallium ions can be derived from a gallium
salt, such as a gallium halide or gallium nitrate compound. The
3-hydroxy-4-pyrone starting materials either occur naturally or may
be obtained commercially or by known synthetic methods. Typical
solvents include water, ethanol, methanol, and chloroform. The
hydroxypyrone and the gallium ions are mixed in 3:1 molar
proportions, preferably with a slight excess of hydroxypyrone to
insure a complete reaction of all the gallium.
Pharmaceutical Compositions and Modes of Administration
[0036] The methods of this invention are achieved by using a
pharmaceutical composition comprising a neutral 3:1 gallium complex
of a 3-hydroxy-4-pyrone. Preferred complexes include, by way of
illustration and not limitation, the 3:1 complex of maltol with
gallium, which is referred to as
tris(3-hydroxy-2-methyl-4H-pyran-4-onato)gallium or gallium
maltolate; and the 3:1 complex of ethyl maltol with gallium,
referred to as tris(3-hydroxy-2-ethyl-4H-pyran-4-onato)gallium or
gallium ethyl maltolate.
[0037] The compounds may be administered orally, parenterally
(including by subcutaneous, intravenous, and intramuscular
injection), transdermally, rectally, nasally, opthalmically,
buccally, sublingually, topically, vaginally, etc., in dosage
formulations containing one or more conventional nontoxic
pharmaceutically acceptable carriers. For example, topical
application to cutaneous lesions, such as the lesions caused by
leprosy, is contemplated. The typical delivery route, however, is
oral.
[0038] Depending on the intended mode of administration, the
pharmaceutical compositions may be in the form of solid,
semi-solid, or liquid dosage forms, such as, for example, tablets,
suppositories, pills, capsules, powders, liquids, suspensions,
creams, ointments, lotions, or the like, preferably in unit dosage
form suitable for single administration of a precise dosage. The
compositions contain an effective amount of the neutral 3:1 gallium
complex of a 3-hydroxy-4-pyrone, generally although not necessarily
in combination with a pharmaceutically acceptable carrier and, in
addition, may include other pharmaceutical agents, adjuvants,
diluents, buffers, etc. Various dosage forms of neutral 3:1 gallium
complexes of a 3-hydroxy-4-pyrone suitable for use in the methods
of the instant invention are set forth by Bernstein, U.S. Pat. No.
6,004,951.
[0039] As noted above, preferred compositions herein are oral
formulations, which include delayed release oral formulations.
While the neutral 3:1 complex of gallium with 3-hydroxy-4-pyrones
delivers gallium to the bloodstream from the gastrointestinal
tract, partial dissociation may occur of the neutral 3:1 complex of
gallium with 3-hydroxy-4-pyrone under acidic conditions (generally
at a pH of about 4 or less). Such acidic conditions may be present
in the stomach. The dissociation may result in formation of less
absorbable complexes, together with free hydroxypyrone and ionic
gallium. Accordingly, in order to maintain the orally delivered
gallium in a form that is highly absorbable in the gastrointestinal
tract, the pharmaceutical compositions of this invention may be
formulated to contain a means to inhibit dissociation of this
complex when exposed to the acidic conditions of the stomach. Means
to inhibit or prevent dissociation of this complex when exposed to
the acidic conditions of the stomach are described in detail by
Bernstein, U.S. Pat. No. 6,004,951. Suitable compositions can
include a buffering agent that is effective to shift the
equilibrium towards the neutral 3:1 complex within a mixture of
gallium hydroxypyrone complexes (including the 1:1, 2:1, and 3:1
complexes), which may result when the composition reaches acidic
conditions in the stomach of the individual. Another means of
inhibiting or preventing dissociation is to encapsulate the
pharmaceutical composition in a material that does not dissolve
until the small intestine of the individual is reached, such as
with enteric coated tablets, granules, or capsules, as is well
known in the art.
Methods of Pharmaceutical Treatment
[0040] In general, the therapeutic plasma levels of gallium are
approximately 1 to 5,000 ng/mL, particularly approximately 100 to
1500 ng/mL. Oral doses to achieve these therapeutic levels are
approximately 10 to 2,500 mg of the complex per day, particularly
approximately 100 to 750 mg per day. The complex is preferably
administered in single dose form, but may be administered in
multiple doses per day. The complex also is preferably administered
at least one hour before meals and at least two hours after meals,
but other schedules are also acceptable.
[0041] Treatment of Mycobacterial Infection
[0042] One embodiment of the invention involves treating a patient
infected by a prokaryote of the genus Mycobacterium by
administering to the patient a therapeutically effective amount of
a neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone. The neutral
3:1 (hydroxypyrone:gallium) complex is one in which the
3-hydroxy-4-pyrone is selected from the group of compounds
represented by Formula 1, as defined above. The therapeutically
effective amount is such that a blood plasma gallium concentration
is achieved that is sufficient to enable beneficial treatment of
the infection.
[0043] Of particular interest is treatment of those patients that
have been infected with Mycobacterium tuberculosis or Mycobacterium
leprae.
[0044] In an exemplary dosing regimen, a patient infected by a
prokaryote of the genus Mycobacterium preferably will be given
about 100 to 750 mg/day of the complex for about 30 to 365 days or
longer, the actual duration of therapy being determined by the
specific infection to be eradicated. Another exemplary dosing
regimen, for example for treatment of M. tuberculosis includes
administration of 150 to 750 mg/day for about 30 to 180 days. Yet
another exemplary dosing regimen, for example for treatment of M.
leprae includes administration of 150-750 mg/day for about 30 to
365 days.
[0045] Optionally, it may be desired to include additional
therapeutic agents with the neutral 3:1 gallium complex of a
3-hydroxy-4-pyrone. Such additional agents include, by way of
example and not limitation, one or more antimicrobial agents.
Exemplary antimicrobial agents are those that have a known efficacy
against one or more mycobacteria species. These include amikacin,
aminosalicylic acid, azithromycin, capreomycin, ciprofloxacin,
clarithromycin, clofazimine, cycloserine, dapsone, erythromycin,
ethambutol, ethionamide, isoniazid, kanamycin, minocycline,
ofloxacin, protionamide, pyrazinamide, rifabutin, rifampicine,
rifampin, sparfloxacin, streptomycin, trimethoprim
sulfamethoxazole, tobramycin, and viomycin, and combinations
thereof. Particularly preferred are combinations of one or more
agents selected from the group consisting of ethambutol, isoniazid,
pyrazinamide, rifampin, and streptomycin. The term "antimicrobial
agent" is intended to include the compounds identified above, as
well as their pharmaceutically acceptable isomers, salts, hydrates,
solvates, esters, and prodrug derivatives, e.g., isoniazid
hydrazide.
[0046] Treatment of mycobacterial infection in combination with
existing therapies
[0047] Another embodiment of the invention involves an improved
method of treating a patient infected by a prokaryote of the genus
Mycobacterium by administering to the patient a combination of
antimicrobial agents selected from the group consisting of
amikacin, aminosalicylic acid, azithromycin, capreomycin,
ciprofloxacin, clarithromycin, clofazimine, cycloserine, dapsone,
erythromycin, ethambutol, ethionamide, isoniazid, kanamycin,
minocycline, ofloxacin, protionamide, pyrazinamide, rifabutin,
rifampicine, rifampin, sparfloxacin, streptomycin, trimethoprim
sulfamethoxazole, tobramycin, and viomycin; the improvement
comprising administering a therapeutically effective amount of a
neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone. The neutral
3:1 (hydroxypyrone:gallium) complex is one in which the
hydroxypyrone is selected from the group of compounds represented
by Formula 1, as defined above. The therapeutically effective
amount is that which achieves a blood plasma gallium concentration
that is sufficient to facilitate the antimicrobial combination
therapy.
[0048] Of particular interest is treatment of those patients that
have been infected with Mycobacterium tuberculosis or Mycobacterium
leprae.
[0049] Particularly preferred for co-administration with the
gallium hydroxypyrone complex are combinations of one or more
agents selected from the group consisting of ethambutol, isoniazid,
pyrazinamide, rifampin, and streptomycin.
[0050] Treatment of mycobacterial infection in an immunocompromised
patient
[0051] Another embodiment of the invention involves treating an
immunocompromised patient infected by a prokaryote of the genus
Mycobacterium by administering to the patient a therapeutically
effective amount of a neutral 3:1 gallium complex of a
3-hydroxy-4-pyrone. The neutral 3:1 (hydroxypyrone:gallium) complex
is one in which the hydroxypyrone is selected from the group of
compounds represented by Formula 1, as defined above. The
therapeutically effective amount is that which provides a blood
plasma gallium concentration that is sufficient to facilitate the
antimicrobial combination therapy, while not creating any
additional complications in the immunocompromised patent.
[0052] Of particular interest is treatment of those patients that
have been infected with species such as M. tuberculosis and M.
leprae, as well as species such as M. avium, M. aurum, and M.
smegmatis, which may pose a health risk to immunocompromised
patients.
[0053] In an exemplary dosing regimen, an immunocompromised patient
infected by a pathogenic species of Mycobacterium will be given
about 100 to 750 mg/day of the complex, for about 30 to 365 days,
or longer. In addition, it may be desired to include additional
therapeutic agents with the neutral 3:1 gallium complex of a
3-hydroxy-4-pyrone in the treatment of an immunocompromised
patient. Such additional agents include, by way of example and not
limitation, one or more antimicrobial agents listed previously
herein.
[0054] The complex may also be co-administered with other
therapeutic agents that the immunocompromised patient may already
be taking. These include, by way of illustration and not
limitation, antiretroviral agents, particularly those used in AIDS
therapy, including without limitation nucleoside analogs such as
zidovudine (AZT), ddI and ddC; protease inhibitors such as
saquinavir, ritonavir, indinavir, and nelfinavir; and
non-nucleoside reverse transcriptase inhibitors such as nevirapine
and delavirdine; and so forth. In considering combination therapy,
it is important to evaluate how the various therapeutic agents
might interact. Many of the aforementioned drugs are nucleoside
analogs, which inhibit polymerization of DNA as it is replicated.
Gallium is expected to work synergistically with these nucleoside
analogs. Gallium inhibits ribonucleotide reductase, and thus
inhibits the production of the nucleosides required for DNA
synthesis. As a result, the relative proportion of nucleoside
analogs to native nucleosides will increase, which will further
inhibit bacterial and retroviral DNA synthesis.
[0055] The treatment of an immunocompromised patient with a gallium
complex containing a 3-hydroxy-4-pyrone is not limited to those
patients whose immunodeficiency is associated with retroviral
infection (such as patients with HIV infection). The gallium
complexes of the present invention can also be effectively
administered to other classes of patients with an immunocompromised
status, such as those undergoing organ transplant or those
suffering from an immunodeficiency of genetic origin.
[0056] An acknowledged advantage of combination therapy is that it
reduces the emergence of resistant strains, due to the low
probability of a single organism simultaneously acquiring multiple
mutations that would confer resistance to each of the administered
agents. The greater the structural and mechanistic differences
between the combined agents, the lower the likelihood that
simultaneous multiple resistance-conferring mutations will arise.
As a primary mechanism of gallium action is novel (the disruption
of bacterial iron uptake and metabolism), the addition or
substitution of gallium to an existing combination therapy regimen
therefore reduces the probability that drug resistance will
develop.
[0057] Prevention of Mycobacterial Infection
[0058] Another embodiment of the invention involves the
prophylactic treatment of a patient to prevent infection by a
prokaryote of the genus Mycobacterium by administering to the
patient a prophylactically effective amount of a neutral 3:1
gallium complex of a 3-hydroxy-4pyrone. The neutral 3:1
(hydroxypyrone:gallium) complex is one in which the hydroxypyrone
is selected from the group of compounds represented by of Formula
1, as defined above. The therapeutically effective amount is such
that a blood plasma gallium concentration is provided that is
sufficient to enable prevention of the infection.
[0059] Of particular interest is the prevention of infection with
Mycobacterium tuberculosis. The method of the invention can be used
to administer a neutral 3:1 gallium complex of a 3-hydroxy-4-pyrone
to uninfected individuals, including but not restricted to patients
that are known to have been exposed to M. tuberculosis or to
individuals or patients who may come in contact with infected
individuals, such as social workers, health care professionals, and
so forth.
[0060] In an exemplary dosing regimen, a prophylactically effective
dose will be about 20 to 500 mg/day of the complex, for about 30 to
180 days, which is the time frame needed for effective prophylaxis.
In another exemplary dosing regimen, a preventative dosage against
a mycobacterial species is about 150 to 750 mg/day of the complex,
for about 30 to 180 days.
[0061] It is to be understood that while the invention has been
described in conjunction with the preferred specific embodiments
thereof, the foregoing description, as well as the examples that
follow, are intended to illustrate and not limit the scope of the
invention. Other aspects, advantages, and modifications will be
apparent to those skilled in the art to which the invention
pertains.
[0062] All patents, patent documents, and publications cited herein
are hereby incorporated by reference in their entirety for their
disclosure concerning any pertinent information not explicitly
included herein.
EXAMPLES
[0063] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how to make and use the compounds of this invention,
and are not intended to limit the scope of what the inventor
regards as his invention. These examples focus primarily on gallium
maltolate or gallium ethyl maltolate as representative complexes of
a 3-hydroxy-4-pyrone with gallium as claimed in the present
invention and should not be regarded as restrictive with respect to
the preferred choice of a 3-hydroxy-4-pyrone. Efforts have been
made to ensure accuracy with respect to numbers (e.g., amounts,
temperature, etc.) but some errors and deviations should be
accounted for. Unless otherwise indicated, parts are parts by
weight, temperature is in degrees Celsius, and pressure is at or
near atmospheric. All solvents were purchased as HPLC or reagent
grade and, where appropriate, solvents and reagents were analyzed
for purity using common techniques. Also, in the x-ray fluorescence
and diffraction data given in Examples 1 and 2, the numbers in
parentheses after the value reported represent the estimated
standard deviation in the last digit(s).
Example 1
Preparation of Gallium Ethyl Maltolate
[0064] A 1.5M solution of ethyl maltol in chloroform was mixed with
an equal volume of a 0.5M solution of gallium nitrate nonohydrate
in ethanol to provide a 3:1 molar ratio of ethyl maltol to gallium
ions in the mixture. The mixture was stirred for 7 minutes at
22.degree. C. Solid anhydrous sodium carbonate was then added in a
10 molar excess, and stirring continued for an additional ten
minutes. When the sodium carbonate was added, a trace of water was
added to facilitate the reaction. The mixture was then filtered and
the filtrate evaporated to give the solid 3:1 complex of ethyl
maltol and gallium. The complex as so produced contained 14.3(1) wt
% gallium by x-ray fluorescence analysis, as predicted for
Ga(C.sub.7H.sub.6O.sub.3).sub.3. The complex formed white to pale
beige monoclinic crystals with unit cell parameters of about
a=7.899(1).ANG., b=8.765(1).ANG., c=31.626(2).ANG.,
beta--103.253(7) degrees, V=2131 .ANG..sup.3, based on powder x-ray
diffraction analysis. The solubility of this compound was measured
as about 5 millimolar in distilled deionized water at 23.degree.
C.
Example 2
Preparation of Gallium Maltolate
[0065] Maltol was dissolved in chloroform to form a 0.75M solution,
and gallium nitrate nonohydrate was dissolved in ethanol to form a
0.5M solution. To 20 mL of the 0.75M maltol solution in chloroform
was slowly added, with continuous stirring, 10 mL of the 0.5M
gallium nitrate nonohydrate solution in ethanol. The resulting
solution was stirred for 5 minutes at 23.degree. C. About 5.5 grams
of powdered anhydrous sodium carbonate were added, and stirring
continued for an additional 12 minutes. The mixture was filtered to
remove all solids, and the filtrate was evaporated in a rotary
evaporator. The remaining crystalline solid was the 3:1
maltol:gallium complex. This complex was analyzed using powder
x-ray diffraction and found to consist of orthorhombic crystals
with unit cell dimensions of about a=8.52(1).ANG., b=16.94(1).ANG.,
c=12.02(1).ANG.. The solubility of this composition was measured as
about 24 millimolar in distilled deionized water at 23.degree.
C.
Example 3
Treatment with Oral Gallium Maltolate of Guinea Pigs Infected with
Mycobacterium tuberculosis
[0066] The efficacy of gallium maltolate in the treatment of M.
tuberculosis infection was studied using male Hartley guinea pigs
(average weight 700 mg). Twelve animals received an aerosol dose of
1.1.times.10.sup.5 CFU (colony forming units) of the Erdman strain
of M. tuberculosis (the same organism that infects humans). This
dose resulted in the implantation of 75-100 bacteria in the lungs.
Each animal was housed in its own cage and was supplied with
HEPA-filtered air. Seven days after infection, the twelve guinea
pigs were divided into four equal groups. Each group received a
different daily dose of gallium maltolate: 0 (control), 3.3 mg/Kg,
10 mg/Kg, and 30 mg/Kg. The appropriate amounts of gallium
maltolate were dissolved in 5 mL of deionized, ultrafiltered water
and the resulting solutions were administered manually to the
guinea pigs by oral gavage. The weight of each animal was measured
each day. Twenty-one days after infection, the twelve guinea pigs
were sacrificed. Necropsies were performed to assess the extent of
disease. The lungs, livers, and spleens in particular were
observed. The spleens were weighed and tissue samples taken for
bacterial culturing.
[0067] All of the gallium maltolate-treated animals had strikingly
fewer tubercules (white, partially calcified nodules resulting from
M. tuberculosis infection) in the lungs and livers relative to the
untreated animals. In addition, cultures taken from the spleens
showed a five-fold decrease in CFUs for the 3.3 mg/Kg dose group
compared to the controls, while the 10 mg/Kg and 30 mg/Kg dose
groups showed a ten-fold decrease. These decreases in CFUs are
greater than those observed for ethambutol and slightly less than
those observed for isoniazid. The results of this experiment show
that orally administered gallium maltolate, even at low daily
doses, is effective in treating M. tuberculosis infection in the
guinea pig, which is an accepted and preferred animal model for
studying the human disease.
Example 4
Preparation of Capsules Containing a Pharmaceutically Acceptable
Buffer
[0068] The purpose of this example is to demonstrate the
preparation of an orally deliverable pharmaceutical composition
containing a neutral complex of gallium and a 3-hydroxy-4-pyrone,
where the means to inhibit dissociation of the complex in the
acidic conditions of the stomach is the use of a pharmaceutically
acceptable buffer. Specifically, 50 mg of gallium maltolate, about
50 to about 1000 mg (preferably 500 mg) of calcium carbonate, and
an amount of starch sufficient to complete filling of a standard
gelatin capsule, are added to a standard gelatin capsule. The
capsule is then closed to provide a composition of this invention.
Such a capsule will inhibit the dissociation of the 3:1
maltol:gallium composition (gallium maltolate) in the acidic
conditions of the stomach.
[0069] In view of the above, other neutral complexes of gallium and
3-hydroxy-4-pyrones could be prepared using the methods described
above by merely substituting such other 3-hydroxy-4-pyrones for
maltol. Similarly, other means to prevent dissociation of the
neutral complex could be employed by merely substituting such other
means for the means exemplified above.
[0070] Specifically, from about 50 to about 1000 mg of other
pharmaceutically acceptable buffers or salts can be employed in
place of calcium carbonate. Such other pharmaceutically acceptably
buffers or salts include, by way of example, sodium bicarbonate,
sodium carbonate, and the like.
Example 5
Clinical Evaluation of Gallium Maltolate for Treating Pulmonary M.
tuberculosis Infection in Combination with Known Therapies
[0071] Gallium maltolate is evaluated clinically for efficacy in
treating M. tuberculosis infection. Adult patients with sputum
smear-positive pulmonary tuberculosis are selected for the study.
The methods employed in this clinical study would be those
described in Kennedy et al., "Randomized controlled trial of a drug
regimen that includes ciprofloxacin for the treatment of pulmonary
tuberculosis," Clin. Infect. Dis. 22(5):827-33 (1996).
[0072] Patients with M. tuberculosis infection are treated once per
day with known therapies along with gelatin capsules containing
gallium maltolate. Patients are divided randomly and blindly into
two approximately equal groups (Group 1 and Group 2). These two
groups are each then subdivided into four approximately equal
subgroups that receive either 0 (placebo), 125, 250, or 500 mg/day
gallium maltolate for about six months. The patients in Group 1
receive the gallium maltolate dose in addition to a combination
anti-tuberculosis therapy of: 300 mg/day isoniazid, 600 mg/day
rifampin, and 15 mg/Kg/day ethambutol. The patients in Group 2
receive the gallium maltolate dose in addition to a combination
anti-tuberculosis therapy of: 300 mg/day isoniazid and 750 mg/day
ciprofloxacin. Patients are monitored for the bacteriological
presence of M. tuberculosis in sputum smears and cultures. Patients
are also medically monitored for M. tuberculosis disease, including
examination for medical symptoms of M. tuberculosis infection such
as possible detection of pulmonary cavitation and/or calcification
by x-ray examinations throughout the study. The sputum smears and
cultures and medical examination are done after the first week, the
second week, and every two weeks thereafter. In addition, lung
histopathology is studied using biopsy, immunostaining and
bacteriological culturing, with lung biopsy samples obtained from
the patients at 0, 30, 90, and 180 days following initiation of
therapy, sampling in regions showing, or previously showing,
radiologic evidence of tuberculosis.
[0073] Experimental clinical work conducted according to the
aforementioned procedures can be used to evaluate the efficacy of
gallium maltolate and related compounds of this invention for
treating M. tuberculosis infection in combination with known
therapies. It is expected that the gallium complexes of the
invention will be shown to be effective additions to any and all
combination therapy regimes, including the two combination
therapies described in the preceding paragraph, with no adverse
effects attributable to the addition of these agents to either
regime. Addition of gallium in particular is expected to shorten
the course of treatment; such a shortening of treatment should
increase patient compliance and thus further decrease the
likelihood that drug resistance will emerge.
Example 6
Preparation of Enteric Coated Capsule Formulation
[0074] The purpose of this example is to demonstrate the
preparation of an orally deliverable pharmaceutical composition
containing a neutral complex of gallium and a 3-hydroxy-4-pyrone,
where the means to inhibit dissociation of the complex in the
acidic conditions of the stomach is the use of an enteric coating.
Enteric coating of a gallium:3-hydroxy-4-pyrone complex is
anticipated to retard or inhibit release of the complex in the
acidic conditions of the stomach and allow the complex to be
specifically released into the contents of the intestine and distal
to the stomach. Specifically, into a standard size 3 hard gelatin
capsule (about 15.5 mm long and 5.8 mm diameter) is added 40 mg of
a 3:1 maltol:gallium composition, 10 mg of maltol, and about 190 mg
of starch. The capsule is closed and is then coated with a layer of
cellulose acetate phthalate/diethyl phthalate using a pilot-scale
procedure described by Jones, Manufacturing Chemist & Aerosol
News 41:43-57 (1970). Acetone is used as a solvent, and a coating
thickness of about 35 micrometers is obtained. Such a capsule
inhibits the release of its contents (the 3:1 maltol:gallium
composition) in the acidic conditions of the stomach, but releases
its contents in the small intestine, where the pH is greater than
about 5.5. Other materials well known in the art can be used to
enterically coat the capsule by merely substituting another
suitable material for the cellulose acetate phthalate/diethyl
phthalate employed above. Such other materials include, by way of
example, cellulose acetate phthalate, hydroxypropyl methylcellulose
phthalate, poly(vinyl acetate phthalate), hydroxypropyl
methylcelluloseacetate succinates, poly(meth)acrylates, and the
like.
Example 7
Clinical Evaluation of Gallium Maltolate for Preventing M.
tuberculosis Infection in HIV Infected Persons
[0075] Gallium maltolate is evaluated clinically for efficacy in
treating M. tuberculosis infection in HIV infected patients. The
clinical methods employed in this clinical study are described in
Gordin et al., "Rifampin and pyrazinamide vs. isoniazid for
prevention of tuberculosis in HIV-infected persons: an
international randomized trial," JAMA 238(11): 1445-50 (2000).
Patients with HIV infection are treated once per day with
enteric-coated capsules containing gallium maltolate. For HIV
disease solely, the patients are also given 300 mg AZT twice per
day, 200 mg ddI twice per day, and 800 mg indinavir every eight
hours. The patients are selected for TB-negative status by skin
test and lung x-ray status, and sputum smear and cultures. Patients
are divided randomly and blindly into approximately six equal
groups, with the first four groups receiving: Group 1: 0 (placebo);
Group 2: 250; Group 3: 500; and Group 4: 750 mg/day gallium
maltolate for about six months. These first four groups of patients
are compared to the last two groups of HIV patients who receive:
Group 5: isoniazid, 300 mg/d with pyridoxine hydrochloride (B
vitamin supplement); Group 6: rifampin, 600 mg/d and pyrazinamide
20 mg/kg per day. Patients are medically monitored for symptoms of
HIV infection and for new M. tuberculosis infection throughout the
study. In addition, blood serum samples are obtained from the
patients at days 0, 30, 90, and 180 and are assayed for CD4 and CD8
T-cell counts by routine methods and for HIV-1 RNA (viral load
assay) using the Roche AMPLICOR assay (Sun et al., J. Clin.
Microbiol. 36(10):2964-2969 (1998)). The primary end point for M.
tuberculosis pathogenesis is culture-confirmed tuberculosis, with a
secondary end point being proven or probable tuberculosis.
[0076] Experimental work conducted according to the aforementioned
procedures can be used to evaluate the efficacy of gallium
maltolate and related compounds of this invention for both treating
HIV infection and preventing M. tuberculosis infection. It is
expected that patients in Group 2, Group 3, Group 4, Group 6, Group
7, and Group 8 will be statistically less likely to have
tuberculosis in conjunction with increased CD4 T cell counts
compared to Group 1 and Group 5.
Example 8
Clinical Evaluation of Gallium Maltolate for Treating M. leprae
Infection in Combination with Known Therapies
[0077] Gallium maltolate is evaluated clinically for efficacy in
treating M. leprae infection. Adult patients with nasal
smear-positive leprosy infections are selected for the study.
Multibacillary (or lepromatous) leprosy is characterized by large
numbers of organisms, and is generally difficult to treat because
of the high likelihood that drug-resistant organisms will emerge
(Katzung, Basic and Clinical Pharmacology, 1998 Apppleton &
Lange, Simon & Schuster). The standard regimen of multidrug
therapy for multibacillary Hansen's disease (leprosy) typically
lasts 24 months and employs three agents: dapsone (100 mg),
clofazimine (50 mg) (both administered daily) and rifampin (600 mg)
(administered monthly with an additional dose of clofazimine (300
mg)).
[0078] The methods employed in this clinical study are described by
Baohong et al., "Bactericidal Activity of Single Dose of
Clarithromycin plus Minocycline, with or without Ofloxacin, against
Mycobacterium leprae in Patients," Antimicrob Agents Chemother
40(9):2137-41 (1996). The efficacy of supplementing treatment for
patients with M. leprae infection by treatment once per day with
enteric coated capsules containing gallium maltolate is evaluated.
Patients are divided randomly and blindly into two groups, Group 1
and Group 2. Each of these two groups is then subdivided into four
approximately equal subgroups, which receive either 0 (placebo),
250, 500, or 750 mg/day gallium maltolate for the first 12 months
of infection therapy. Group 1 receives the gallium complex as
indicated, in addition to the traditional combination anti-leprosy
therapy of: 100 mg/day dapsone; 50 mg/day clofazimine; 600 mg
rifampin once monthly together with an additional dose of 300 mg
clofazimine. Group 2 also receives the gallium complex as
indicated, in addition to the alternative combination anti-leprosy
therapy of: a monthly dose of 600 mg rifampin, 1600 mg
clarithromycin, 160 mg minocycline, and 650 mg ofloxacin. All
patients are monitored for the bacteriological presence of M.
leprae in nasal smears and cultures. Patients are also medically
monitored for M. leprae disease, including: examination for medical
symptoms of M. leprae infection, including cutaneous and neural
manifestations of disease; histopathologic examination of biopsy
tissue; and "culturing" of all identified lesions by mouse footpad
inoculation (Dhople et al., Indian J. Lepr. 63(2):166-79 (1991);
and Dhople et al., Arzneimittelforschung 41(3):253-56 (1991)). The
smears, cultures, and medical examinations are performed after the
first week, the second week, and every two weeks thereafter. In
addition, cutaneous lesion biopsy samples are obtained from the
patients at 0, 30, 90, and 180 days, and every 90 days thereafter.
Lesion histopathology is studied using immunostaining and
bacteriological culturing.
[0079] Experimental work conducted according to the aforementioned
procedures can be used to evaluate the efficacy of gallium
maltolate and related compounds of this invention for treating M.
leprae infection. It is expected that the gallium complexes of the
invention will be effective additions to one or both of the studied
combination therapy regimes, with no adverse effects attributable
to the addition of these agents to either regime. Addition of
gallium is expected to shorten the course of treatment in both
regimes.
* * * * *